Many mobile communication terminals such as cell-phones generally are of a folding type or of a sliding type comprising multiple movable casings for portability and operability.
The display units used in mobile communication terminals are dominantly composed of liquid crystal display panels. Some of such display units have the touch panel function, namely, numeric keypads and other buttons used for input operation are realized as software keys.
Presumably, the physical buttons can be replaced with software keys in the folding or sliding type devices. In such a case, more diverse display modes can be realized by coupling two or more display screens.
Furthermore, three-dimensional image display techniques utilizing liquid crystal display technique have been established (for example, the Japanese Patent No. 2857429). In such three-dimensional image display techniques, the viewing position (head position) of the user is detected and the three-dimensional images are so formed as to trace the viewing position for maintaining excellent three-dimensional display (for example, Unexamined Japanese Patent Application KOKAI Publication No. H10-333091).
Compared with the prior art one-screen three-dimensional display, more diverse effects can be realized by applying the three-dimensional display technique to two or more coupled display screens.
A drawback of three-dimensional images is that they are difficult to view unless the display is controlled in accordance with the viewing conditions (such as the viewing distance and angle and the interocular distance of the viewer). In a folding or sliding type device, the viewing condition is altered when the coupling state between the two screens is changed, leading to failure to maintain an excellent three-dimensional display.
The technique described in the Unexamined Japanese Patent Application KOKAI Publication No. H10-333091 can be used in order to eliminate the above inconvenience. However, a position-detecting sensor is necessary for detecting the viewing position (the head position) and allowing the three-dimensional image to trace it and the parameters for the tracing become multifaceted. Therefore, the hardware configuration and software processing becomes complex. It is difficult to apply such a technique to a small device such as a mobile communication terminal. Furthermore, additional complex processing is required in applying such a technique to two or more coupled display screens; such application is much more difficult.